Photographic silver halide diffusion transfer process



United States Patent 3,017,270 PHOTOGRAPHHC SILVER HALKDE DIFFUSIQN TRANSFER PROCESS Leonard W. Tregillns and Arthur A. Rasch, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Mar. 31, 1958, Ser. No. 724,828 3 Claims. (Cl. 96-29) This invention relates to the silver halide diffusion transfer process of photography and more particularly to methods for increasing the speed of the process and density of reproductions obtained thereby.

In the well-known silver halide diffusion transfer process of photography, an exposed emulsion layer is developed in the presence of a silver halide solvent, the emulsion layer being for at least a portion, or for the whole of the development period in effective contact with a receiving sheet, the surface of which generally carries a quantity of a silver precipitant which may comprise either physical development nuclei such as colloidal silver or silver sulfide or a chemical precipitant for silver ions, such as zinc sulfide, Development of the emulsion layer proceeds and is followed immediately by complexing of the residual unexposed silver halide with a silver halide solvent also present in the developer composition, and imagewise diffusion of the resulting silver complex to the receiving sheet where the silver precipitant causes the formation of an argental (of or containing silver) image.

We have discovered that when the silver halide diffusion transfer process is carried out in the presence of certain onium compounds including certain quaternary ammonium and ternary sulfonium salts, a number of improvements are unexpectedly obtained. These improvements include increase in density of the positive image, appreciable increase in emulsion speed and rate of development, and change in tone of the positive image from a warm brown to a neutral black color. These effects are separate and distinct from the effects of amines and the lower alkyl quaternary ammonium hydroxides in silver halide solvent transfer processes. Furthermore, in the presence of the onium compounds an increase in solvent action of the silver halide solvent is observed. Accordingly, it is possible to use an appreciably smaller amount of the silver halide solvent or a weaker silver halide solvent than the conventional sodium thiosulfate in the process without experiencing loss of density in the positive image. Also the effect of the quaternary nitrogen compounds and ternary sulfonium compounds in the diffusion transfer process has been found to be separate and distinct from comparable usage of the compounds in connection with emulsions subjected to the older methods of simple development and fixation. For example, in the Piper U.S. patent application Serial No. 550,495, filed December 1, 1955, now US. Patent No. 2,886,437, granted May 12, 1959, quaternary ammonium compounds are utilized together with polyalkylene oxides to increase emulsion sensitivity over that attributable to the polyalkylene oxides themselves. However, when such quaternary nitrogen compounds are used in the present invention as illustrated hereinafter, emulsion speeds generally as high or higher are obtained in the absence of the polyalkylene oxide compound.

We have further discovered that in addition to effecting the mentioned improvements in the silver halide diffusion transfer processes, when the quaternary ammonium salts are employed in the diffusion transfer processes in conjunction with certain tone-modifying compounds, pronounced improvement in image toneof the argental images formed in the processes is obtainable even though the processes are carried'out at moderately low pH. That is, the silver halide diffusion transfer processes are ordinarily carried out using developer solutions having relatively high pH of the order of 12 so as to maintain a high development rate necessary for the proper functioning of. the process. It is desirable to operate the diffusion transfer processes at lower pH partly because the developers of low alkalinity produce less skin irritation, are less costly, handle better, and the print quality is improved. However, at moderately low. pH of the order of 10, the tone of they argental image is characteristically warm brown. This is true even if tonemodifying compounds such as the mercaptotetrazoles are employed in the emulsion, the developer or both. Accordingly, when the quaternary salt compounds and certain tone modifying compounds described hereinafter are present at the time the argental image is being formed in the receiving sheet, a profound improvement of the image tone is obtained, i.e. shift in color of the argental image from brown to black, and this effect is obtainable even when carrying out the diffusion transfer processes with stable alkaline developer compositions of pH of the order of about 10 to 10.4. This degree of improvement in image tone cannot be obtained in such solutions by use of the quaternary salt alone in any concentration or by use of the tone'modifying compound alone in any concentration.

The objects of the invention therefore include providing means for increasing the effective speed ofdiffusion transfer processes, means for improving the tone of the prints obtained in the diffusion transfer processes and means for carrying out the diffusion transfer processes at moderate pH. Other objects of our invention will be: come apparent from the following description thereof.

These objects of the invention are accomplished in part by providing suitable emulsions, developer solutions and receiving layers and carrying out diffusion transfer processes therewith in the presence of quaternary ammonium or ternary sulfonium compounds alone or additionally in the presence of certain tone modifying compounds.

The onium compounds of the invention which are used in the diffusion transfer processes are quaternary ammonium and ternary sulfonium compounds, the onium radical of which has attached to it a chain containing at least 7 atoms such as carbon atoms, carbon atoms and oxygen atoms, etc. Included among the onium com pounds are the following representative groups of compounds:

(A). Trialkyl sulfonium salts in which one of the alkyls contains at least 7 carbon atoms. These sulfonium salts have the general structure where:

R and R represent alkyl groups, e.g., methyl, cat-boxymethyl, ethyl, propyl, butyl, etc., 'or aralkyl group's, e.g., benzyl,

R represents an alkyl group of at least 7 atoms, e.g., heptyl, nonyl, decyl, dodecyl, tetradecyl, cetyl, etc., and

X represents an anion, e.g., chloride, bromide, iodide,

perchlorate, p-toluene sulfonate, alkyl sulfate, etc. Specific compounds having the above formula are:

suit. I Dimethyl n-dodecyl sulfonium p-toluene sulfonate 'Sulf. II Dimethyl n-heptyl sulfonium. p-toluene sulfonate Sulf. III Dimethyl n-nonyl sulfonium p-toluene sulfonate Sulf. -IV Dimethyl n-decyl sulfonium p-toluene sulfonate Sulf. V Dimethyl n-te tradecyl sulfonium p-toluene sulfonate Other useful compounds having the above general formula are described in the Carroll and Allen US. Patent 2,275,727, granted March 10, 1942.

(B) Polysulfonium salts having the general structure R: ZRz 2 wherein R and R are as above indicated and Z represents a bivalent organic radical such as the ethylene-bis-oxymethyl radical present, for example, in the compound ethylene-bis-(oxymethyl dodecyl methyl sulfonium ptoluene sulfonate) Sulf XIV Other suitable polysulfonium salts are disclosed by the Carroll and Allen U.S. Patent 2,288,226, granted June 30, 1942.

(C) T etraalkyl quaternary ammonium salts having the general formula in which X is an anion or acid radical, for example, halide, p-toluene sulfonate, alkyl sulfate or perchlorate, R, R R and R are alkyl groups of which at least one has a chain or seven or more atoms such as carbon atoms, carbon atoms plus oxygen atoms, sulfur atoms or nitrogen atoms and ring systems, while the remaining R groups are alkyl such as methyl, ethyl, butyl, and benzyl as exemplified hereinafter.

In addition, the quaternary nitrogen atom may be linked through one of the R groups to a second quaternary nitrogen atom as in the bis-quaternary ammonium salts having the general structure wherein R, R and R are as just mentioned and Z is a bivalent radical as exemplified by those radicals disclosed in US. Patent 2,288,226, for example, the decamethylene radical.

(D) Quaternary ammonium salts in which the quaternary nitrogen atom is a part of a ring system and which have the general formula C NR X where X is as above mentioned and R represents a chain of at least seven atoms and Z represents the atoms necessary to complete a cyclic structure such as a pyri dyl, apicolyl, piperidyl or morpholinyl nucleus. R may contain a second quaternary nitrogen atom as present in the bis-quaternary ammonium compounds having the structure 4 Compounds illustrative of classes C and D compounds above are as follows:

Decamethylene-a-w-bis(oxymethylpyridinium perchlorate) Laurylpyridinium perchlorate Decamethylene-bis-(oxymethyl a picolinium perchlorarate) p-Xylylene-bis-(pyridinium perchlorate) HeXamethylene-bis(oxymethylpyridinium perchlorate Hexadecylpyridinium bromide Decamethylene bis(oxymethyldimethylbenzylammonium perchlorate) Decamethylene-bis(N-methylpiperidinium perchlorate) Lauryl pyridinium-p-toluenesulfonate N-n-tetradecyl-N-methylmorpholinium-p-toluene sulfonate Lauryl trimethylammonium-p-toluene sulfonate n'Myristyl-trimethylammonium-p-toluene sulfonate Decamethylene-bis-trimethylammonium bromide Decamethylene-bis-triethylammonium perchlorate Tetradecamethylene-bis (pyridinium perchlorate) (E) Cationic polyalkylene oxide salts used alone or with a stabilizing agent such as an azaindene compound as described in the Carroll et al. US. patent application Serial No. 627,135, filed December 10, 1956.

These ionic polyalkylene oxide compounds include cationic materials such as quaternary ammonium and phosphonium polyalkylene oxide salts, and ternary sulfonium polyalkylene oxide salts; and anionic polyalkylene oxide compounds such as the polyalkylene oxide carboglutamic acid salts, polyalkylene oxide-bis-N-carboxymethyl carbamate salts, polyalkylene oxide-bis-sulfuric acids, etc.

The cationic quaternary and ternary polyalkylene oxide salts used in the invention are characterized as containing bivalent polyalkylene oxide radicals such as corresponding to polyethylene oxide, polypropylene oxide and polybutylene oxide radicals to which is attached at least one onium salt group such as a quaternary ammonium, phosphonium or ternary sulfonium salt group, and wherein n is a positive integer at least as great as 4 representing the least number of alkylene oxide units present in the polyalkylene oxide radical of the salt.

A representative cationic salt is octaethoxy ethyl-bispyridinium perchlorate having the following formula:

(F) Bis-quaternary salts Whose quaternary nitrogen atoms are connected by means of a linear chain containing less than 34 atoms such as bis-amide, bis-urethane, bis-urea, bis-ester, etc. compounds having the following general formulas:

wherein Q and Q represent organic radicals containing quaternary nitrogen atoms, R and R represent alkylene groups, R represents an alkyl group of from 1 to 4 carbon atoms, n represents a positive integer of from 1 to 2, A represents a chain of atoms of the class consisting of carbon, nitrogen, oxygen and sulfur atoms, there being less than 34 atoms present in the linear chain connecting Q to Q.

These compounds are described in more detail in the Beavers, Wilson and Graham US. patent applications Serial Nos. 699,197, 699,198 and 699,199, filed November 27, 1957, now respectively U.S. Patents 2,940,851 granted June 14, 1960, 2,944,898 granted July 12, 1960, and 2,940,855 granted June 14, 1960. Representative compounds of this class are as follows:

The anion of the above ammonium and sulfonium compounds may be any acid radical not injurious to photographic emulsions, for example, p-toluene sulfonate, chloride, bromide, iodide, perchlorate or alkyl sulfate. The introduction of halide anions into photographic silver halide emulsions alters the halide concentration in the emulsion and compensating changes in the emulsion may be desirable if such salts are employed. For this reason, it is ordinarily preferred to employ compounds containing anions other than halides. Perchlorates and p-toluene sulfonates are advantageously employed.

The use of the quaternary ammonium compounds in various ways in different solvent transfer processes will now be illustrated by means of the following examples.

In the examples the quaternary nitrogen compounds whose use is illustrated are referred to for convenience as follows:

Quat. 'ITetnadecamethylene-bis(pyridinium perchlorate) Quat. II7,18-diaza-6,19-dioxotetracosane-l,24-bis(pyridinium perchlorate) (Beavers-Wilson invention above) Quat. III3,6,9,12,15,18,21,24-octoxa-hexacosane- 1,26-

bis(pyridinium perchlorate) (Car-roll et al. US. Serial No. 627,135, filed December 10, 1956) Quat. IV-a-Picolinium-fi-phenyl-ethyl bromide In the examples when comparing the effectivness of the quaternary nitrogen compounds present in the emulsion, developer or receiving sheet, the particular emulsion is exposed on an intensity-scale sensitometer and development then initiated at room temperature with a developing solution of the following composition unless otherwise indicated:

Hydroquinone 32.8 Sodium sulfite (anhydrous) 75.0 Sodium thiosulfate 14.0 Sodium hydroxide 26.7 Benzotriazole 0.12

Water to make 1.0 liter.

If desired, p-phenylenediamine may replace the hydroquinone and thiosulfate in the formula since it functions both as a developing agent and as silver halide solvent in the processes described hereinafter.

Following initiation of development the emulsion is then rolled into contact with a receiving sheet containing a suitable silver precipitant and left in contact until an argental image has formed on the sheet from the silver halide transferred thereto.

6 Unless otherwise indicated, the receiving sheet in the examples was prepared as follows: The following solutions were provided:

Jet streams of the two solutions were passed at equal rates into a funnel for rapid mixing, and thereafter the mixture was allowed to trickle through a column packed with glass helices over a period of approximately 12 seconds allowing the mixture to fall into a gelatin solution being stirred rapidly, the gelatin solution comprising 15 grams of gelatin, cc. of water, the temperature being 40 C. The mixing of the solutions required about 5 minutes. To 200 cc. of the resulting dispersion which had been stirred for 1 hour were added 2.8 grams of lead acetate. After 15 minutes of stirring, the pH was adjusted to 3.0 with 6 molar nitric acid and thereafter the composition was coated at a coverage of 2 cc. per square foot on a film base.

The densities of the transferred positive images obtained on the receiving surfaces were read by transmission and from the resulting characteristic curves speeds were measured in units of (l-log E) where E is the exposure in meter-candle seconds required to produce a density of 0.3 above fog. Since the densities were read by transmission and the positive images were designed for viewing by reflection, the effective densities are higher than those shown in the examples. From the data in the examples it will be observed that the maximum eifectivness of the quaternary nitrogen compounds in increasing speed occurs when these compounds are used in the emulsion.

EXAMPLE 1 Addition of quaternary ammonium salt to the emulsion An extremely high-speed bromoiodide emulsion optically sensitized with methyl -3,3-diethyl seleno carbocyanine iodide and chemically sensitized with gold and sulfur compounds was provided. Also there Was added to the emulsion 2 grams per mole of silver halide of 4-hydroxy-6-met'hyl-1,3,3a,7-tetrazaindene (indicated as AZA hereafter). The amounts of the quaternary nitrogen compound indicated in the following table were then added to samples of this emulsion and the samples tested as described above:

Compound Grams per Speed mole AgX EXAMPLE 2 Addition of quaternary ammonium salt to the developer An emulsion similar to that of Example 1 was =pr0- vided except that decamethylene-bis-benzothiazolium perchlorate was used instead of the azaindene stabilizer. The diffusion transfer process described above was carried out using portions of the above standard developer to which the following additions had been made:

one sample of the developer as shown in the following table:

Grams per Grams per Compound liter Speed Compound liter De- D max. Speed Developer veloper 0 325 Sulf. III 0 0. 42 437 0. 03 32s Suli. III 3. 2 0. 77 439 0.1 341 0.3 343 -8 From these data it is apparent that the addition of the M3 sulfonium compound to the developer did not greatly increase speed much but this speed increase was real as 350 substantiated by other tests. 0 0% EXAMPLE 6 013 2554 Addition of quaternary ammonium salt to the emulsion 346 and use of high energy developer Compared to Example 1, the data show that the emulsion of Exflmple 5 was used, a quaternary quaternary compounds are somewhate less effective in the mtrogfm p nd belng added to one sample of the developer than in the emulsion emu1s1on as shown in the table following. In the process the standard developer was modified as follows to ob- EXAMPLE 3 tain maximum development activity: Addition of quaternary ammonium salt G.

to the receiving layer Hydfoqumone Sodium sulfite 80 The emulsion 0f Example 2 WES s and w Sodium hydroxide 2 5 mg amounts of quaternary nitrogen compounds were lll- Hypo 10 corporated into samples of the receiving sheet: g,i gig; g giggg 2 Il'll'g 1111 '1 ansmission 3O g g-i i nitrate V1 1 Tc S T v 1 u te Compound rl fcii v'i' D mum Water to 1 liter.

Compound D max. Speed Quat. II 0 76 430 I Quat. II 0.4 .72 437 When the quaternary ammonium salt 18 mcorporated recewer Its action on development of the As illustrated in the above examples, useful results are negatwe takes place only after F i 40 obtained with about 0.03 to 1.0 gram of the quaternary between the receiver and the negative Whlc has prevl nitrogen compound per mole of silver halide in the emulously been with developer sion or per liter if in the developer.

EXAMPLE 4 The following examples illustrate usage of the ternary Addition of quaternary ammonium salt and stabilizing sulfomum Ompounds m dlfiuswn transfeir Processes agent to the emulsion As mentioned above, the ternary sulfomumcompounds themselves have little solvent action on silver hahde T emulsion of p 1 was used to which had but when employed with a silver halide solvent such as been add the azain'dene Compound above, and hypo, sodium sulfite, potassium thiocyanate or potassium cadmium chloride in the amount 'S in the fOHQWiIIg bromide, the rate of solution of the silver halide through table: complexing with the solvent is increased considerably. Accordingly, in the process a greater amount of the silver Compound Grams per speed halide is made avaliable for formation of the positive mole AgX image on the receiving sheet. Thus, better reproductions are obtained and a smaller amount of silver halide solvent 393 or a weaker silver halide solvent can be used in the 427 system. For example, a developer may be used contain- 32 422 ing /3 to /3 of the usual amount of hypo and a speed 5 427 increase of about 0.45 log E is obtained when the onium 2% compound is also present. Similar effects are obtainable 439 when sodium thiocyanate and to a lesser extent high concentrations (50200 grams per liter) of potassium bromide are substituted for hypo. A weak image can even EXAMPLE 5 be obtained with sodium sulfite in the presence of the onium compound. When the onium compound is used Addmon of asulfomm. salt to the develop? in the developer in concentrations of the order of 1.0 quaternary ammomum salt to the emulsmn gram per liter, an increase in speed of about 0.15 to To a high-speed bromoiodide emulsion optically sensi- 0.30 log E is readily obtainable. At much higher contized as in Example 1 and chemically sensitized with sulcentrations a warmer toned image is obtained with loss fur and gold compounds, were added 2 grams of AZA, of maximum density partly because of development of 0.4 gram Quat. II and 10 grams of cadmium chloride fog in the negative layer which tends to reduce the per mole of silver halide. To the standard develop-er composition given above was added 2.0 grams of l-phenyl- 3-pyrazolidone and 50 grams of xylene sulfonate per liter. A sulfonium compound dimethyl-n-nonyl-sulfonium-p-toluene sulfonate (Sulf. III) was also added to amount of silver halide available for transfer. When employed in the emulsion, it is preferred to maintain fog at a low level by use of antifoggant such as the azaindenes provided below.

The maximum effectiveness of the ternary sulfonium compounds occurs when they are used in the developer compositions and is generally accompanied by either no change or an increase in maximum density of the transferred positive image as compared to a developer free of the sulfonium compound.

EXAMPLE 7 sulfonium compound in developer The receiving sheet was prepared as follows: A solution containing 100 cc. of water and 1 cc. of 0.5 molar sodium sulfide was added in 1 minute and 20 seconds to a solution of 1 cc. of 0.5 molar zinc nitrate and 0.5 cc. of 10 percent gelatin solution in 375 cc. of water at 40 C. Twenty-five cc. of a 10 percent gelatin solution were then added and 1.5 grams of lead acetate and a suitable gelatin hardening agent. The resulting composition was then coated at a coverage of 6 cc. per square foot upon a film support.

The emulsion used was a medium-speed bromoiodide emulsion.

The developer had the same composition as the standard hydroquinone developer given preceding Example 1 except that the hypo was reduced from the normal level of 14 grams to 7.5 grams per liter and 0.95 gram of dimethyl n dodecyl sulfonium p toluene sulfonate was added per liter. The diffusion transfer process of Example 1 was carried out with the result that a speed increase of 0.3 log E in the shoulder regions, a 0.6 log E increase in the toe regions of the characteristic curve, a maximum density increase of about 0.15 and a slightly colder tone was obtained compared to the same emulsion processed in the standard hydroquinone developer free of the sulfonium compound and containing the higher level of hypo. By transmission the increase in density was 0.42.

EXAMPLE 8 Sulfonium compound in developer A receiver was prepared by first mixing rapidly a solution comprising Water cc 1200 0.5 M sodium sulfide cc 6.0

with a solution comprised of- Water cc 4750 Gelatin g 0.9 0.5 M zinc nitrate cc 6.0 0.5 M lead acetate cc 3.0

at 40 C. To 2000 cc. of this solution was added after minutes of stirring 20 grams of gelatin. To 600 cc. of the resulting solution was added after one hour of stir ring 10.5 cc. of a 0.5 M lead acetate solution. This solution was adjusted to a pH of 3.5 with nitric acid, a coating aid and a hardening agent were added, and then the solution was coated on film support at 6.0 cc. per square foot.

The negative consisted of a gelatino-silver bromoiodide emulsion containing 6.3 mole percent iodide, optically sensitized with methyl-3,3-diethyl-seleno-carbocyanine iodide, and containing the antifoggant 4-hydroxy-6-methyl- 1,3,3a,7-tetrazaindene. The emulsion was coated on film support so as to obtain 0.09 g. silver and 0.50 g. gelatin per square foot.

The developer was the same as the standard hydroquinone-control developer except that 0.5 gram per liter of the sulfonium compound of Example 7 was used. When processing was carried out as above, a speed gain of 0.45 log E was realized over the same process in which the sulfonium compound was omitted from the developer. The increase in D max. was 0.15 (by reflection) and 0.07 (by transmission).

10 EXAMPLE 9 Sulfonium compound in emulsion EXAMPLE 10 Sulfonium compound in receiving sheet The emulsion, developer and procedure of Example 7 were employed with the receiving sheet of Example 8 above to the coating of which had been added 1.0 gram of the sulfonium compound of Example 7. An increase in density of 0.15 was obtained in the positive compared to the control process where the sulfonium compound was absent from the receiving sheet. A D max. (transmission) 0.13.

EXAMPLE 11 Sulfonium compound in receiving sheet The process of Example 10 was carried out except that the receiving sheet consisted of a water resistant paper sheet carrying a gelatin coating containing colloidal silver and 15 milligrams of the sulfonium compound of EX- ample 7 per square foot. The image obtained in the positive was brown in color and of significantly higher density compared to a light yellow image contained in the control process using the same receiving sheet free of sulfonium compound. A D max. (transmission) 0.37.

EXAMPLE 12 Sulfonium compound in developer The process of Example 11 was carried out except using 2.0 grams per liter of the sulfonium compound only in the developing solution. The same improvement in image tone was obtained. The maximum density (trans-. mission) was 0.73, compared with 0.16 for the control.

EXAMPLE 13 sulfonium compound in developer The receiving sheet of Example 1 and a fast bromoiodide emulsion were used in the process. The standard hydroquinone developer contained 0.4 gram per liter of Sulf. I. In the transfer process, a speed gain of 0.15 log E was obtained compared to the control process using no sulfonium compound in the developer.

When 1.0 gram per liter of 1-phenyl-3-pyrazolidone was further added to the developer composition containing the sulfonium compound, an additional 50 percent increase in speed was obtained in the process.

EXAMPLE 14 Use of thiocyanate as the silver halide solvent Medium-speed panchromatic bromoiodide emulsion was used with the receiving sheet of Example 1 and the following developer composition:

Grams Hydroquinone 35 Sodium snlfite 80 Sodium hydroxide 218.5 20

Sodium thiocyanate Water to 1 liter.

Addition of 0.2 gram of Sulf. I produced an increase 11 1 in maximum density of 0.15 in the transferred positive image.

EXAMPLE 15 I Sulfonium compound in developer Sulfonium Salt Speed Increase,

A log E From similar tests it has been ascertained that when the sulfonium compounds are present in amounts up to about 2.0 grams per liter of developer, the most significant improvements in speed and other characteristics of the process are obtained. The choice of elements of the process will naturally be found to also influence the optimum amount of sulfonium compound to use and similarly for the above quaternary ammonium compounds.

The azaindene stabilizing agents suitable for use in the invention as indicated above are those such as described in the Carroll et al. US. patent application Serial No. 627,135, filed December 10, 1956, as follows: 4- hydtoxy-6-methyl-l,3,3a,7-tetraazaindene, carboxy-4- hydrox -1,3,3a,7-tetraazaindene (Reynolds et al. U. S. Patent 2,756,147, granted July 24, 1956), 1,2-bis(4- hydroxy-6-methyl-1,3,3a,7 tetraazaindene 5 yl)ethane, 1,2,3,4-tetrakis(4 hydroxy 6 methyl-1,3,3a,7-tetraazaindene-2-yl)butane, 2-amino 5 carboxy-4-hydroxy-1,3, 3a,7-tetraazaindene, 4 hydroxy 2 B hydroxyethyl-6- methyl,l,3,3a,7-tetraazaindene, 5 carbethoxy-4-hydroxyl,3,3a,7-tetraazaindene (Reynolds et al. invention above), 7 hydroxy 1,2,3,4,6 pentaazaindene, 4 hYdIOXY-Z-yhydroxypropyl-6-methy1-1,3,3a,7 tetraazaindene and 4- hydroxy-2(4-pyridyl)-6-methyl-1,3,3a,7 tetraazaindene.

Other azaindene compounds useful for this purpose are disclosed in the examples hereinafter, in US. Patents 2,716,062 and 2,713,541, and in Allen et al. US. Patent 2,735,769, February 21, 1956 Allen et al. US. Patent 2,743,181, April 24, 1956 Tinker et al. US. application Serial No. 515,785, filed June 15, 1955, now US. Patent No. 2,835,581, granted May 20, 1958 Reynolds US. Patent 2,756,147, July 24, 1956 Carroll et al. US. Patent 2,743,180, April 24, 1956 Zeitschrift fiir Wiss. Phot., 47, 2-28 (1952) Additional ingredients useful in the emulsion of the diffusion transfer process of the invention include the noble metal salts of group VIII of the periodic table, gold, salts, reducing agents, mercury compounds and various combinations of silver halides disclosed in the Carroll et al. US. patent application Serial No. 627,135, filed December' 10, 1956, now US. Patent 2,944,902 granted July 7, 1960.

In those cases where the diffusion transfer process involves the development of dye images by means of the paraphenylenediarnine type of developing agents, suitable colored or colorless coupler compounds of the phenolic hydroxyl, pyrazolone and open-chain reactive methylene types may be employed in the emulsion, receiving sheet, or developer.

The quaternary ammonium and ternary sulfonium compounds indicated are similarly beneficial for use with other types of diffusion transfer processes such as that disclosed in the Yackel et al. US. patent application Serial No. 586,705, filed May 23, 1956, wherein a unitary element is provided having, for example, a removable cellulose ether phthalate silver halide emulsion layer coated upon a receiving layer containing a silver precipitant. The quaternary ammonium or ternary sulfonium compound may be present in either the emulsion, the receiving layer or the developer solution. The element is exposed in a suitable manner, development initiated in the presence of a silver halide solvent and a positive image formed in the receiving layer accompanied by removal of the overlying emulsion layer containing the negative image.

Additional well-known silver precipitating agents for use in the processes of the invention of the nature disclosed in the above Yackel et al. invention give useful results in the present process.

When the indicated quaternary ammonium salts are used in the process of the Yackel et al. invention, it is advantageous to also employ one of the azaindene stabilizing compounds preferably together with a tone modifying agent. That is, when a high speed coarse-grained emulsion is to be used containing the cellulose ether phthalate vehicle and a minimum of gelatin, the stability of the emulsion is increased by adding an azaindene compound such as mentioned in Example 9 above. The stability conferred by this compound is greater than obtainable with antifoggant compounds of the benzothiazole and mercaptotetrazole types; however, a loss in D mm is sustained and it is desirable to further add a quaternary nitrogen compound such as Quat. II above to restore D max, and preferably also 2-mercapto-5-phenyl-1,3,4- oxadiazole to improve the tone of the image.

3-pyrazolidone silver halide developing agents which may be employed in the developer composition alone or in conjunction with other silver halide developing agents such as hydroquinone are disclosed in the James US. Patent 2,571,300, granted June 19, 1956, for example, 1-phenyl-4,4-dimethyl-3-pyrazolidone. Such usage of the pyrazolidone compounds may be alone or in conjunction with ascorbic acid for the purposes disclosed in the patent. Also, the silver halide developing agents may be present in the emulsion layer rather than in the alkaline solution containing the silver halide solvent. Thus developer compositions exemplified above containing the combination of a silver halide solvent, a 3-pyrazolidone developing agent, a hydroquinone such as hydroquinone, per se, toluhydroquinone, and chlorohydroquinone, and one of the mentioned quaternary ammonium salts, especially the cyclammonium quaternary salts are especially useful in the diffusion transfer processes.

As mentioned previously, when the quaternary salts are employed in the diffusion transfer processes in conjunction with certain tone modifying compounds, pronounced improvement in image tone is obtainable even when the processes are carried out at moderately low pH. Suitable quaternary salts are those mentioned above. The following quaternary salts are representative cyclammonium quaternary salts, which are particularly effective in combination with the tone modifying compounds.

Tetradecamethylene-bis (pyridinium perchlorate) a-Dimethyldithiocarbamatoethyl-N-methyl pyridinium -ptoluene sulfonate Decamethylene-ot,w-bis-(oxymethyl pyridinium perchlorate) 3,6,9,12,15,18,21,24 octahexacosane 1,26 bis(5-ethyl- Z-methyl pyridinium methane sulfonate) Z-B-phenethylisoquinolinium bromide l-p-phenethylquinolinium bromide 3,14-dioxahexadecane-1,16-bis-(pyridinium methane sulfonate) 13 l-methyl-Z-nonanoyl pyridinium p-toulene sulfonate Heptoxymethyl-Z,4,6-trimethyl pyridinium chloride Tetradecamethylene-bis-(trimethyl ammonium perchlorate) 3-methyl-2-p-phenethyl isoquinolinium bromide 1fi-phenethyl-a-picolinium bromide 4,4,10,10 tetraoxo 4,10 dithiatridecane bis (pyridinium perchlorate) A quaternary ammonium base, ,B-hydroxy ethyl trimethyl ammonium-hydroxide has been used as an agent for promoting photographic quality in solvent transfer processes. However, this compound and other similar quaternary ammonium bases and salts which consist of an onium radical attached to short chain aliphatic groups such as tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, tetra-n-propyl ammonium hydroxide, tetra-kis(2-hydroxy-ethyl)ammonium hydroxide, or the halide, perchlorate, or p-toluene sulfonate salts of these bases, are not suitable for the purposes of this invention.

The mentioned tone modifying compounds which are useful in combination with the quaternary salts, and which are particularly useful in combination with the cyclarnw monium quaternary salts given immediately above, are the following cyclic and open chain sulfur and nitrogencontaining compounds which are characterized as being organic compounds forming with silver ion, such as present during the transfer of dissolved silver halide, a silver compound less soluble than silver bromide in water and solutions of silver halide solvents. It is known that some of these organiccompoundsare useful in controlling the tone of silver images but as mentioned above and shown in the examples hereafter pronounced improvement in tone results when these organic sulfur and nitrogencontaining compounds are used in combination with the onium compounds compared to using either compound alone.

Z-mercaptol-phenyl-tetrazole N r l l N --SE 2*rnercapto-5phenyl-1,3,4 oxadiazole Dihydro-l ,4-benzothiazin-3 one 2-'y-pyridylbenzothiazoline hydrochloride N-H I N .HCl

5-tbutyl-6-rnethyl- 1 ,2,3.a,7-tetraz1aindene-4-thiol N N CH3 t-C4H l 4 7-seleno-1,3 ,4,6-tetrazaindene SeH H r Y W KW 2,6-dimethy1-1,3,3 a,7-tetrazaindene-4-thiol on; i f m-om SH 5-ethyl-6-methyl-l,2,3a,7-tetrazaindene-4-thiol CH3 Y C2H'5 \y SH bis( 5 p-hydroxyphenyl-l 3,4V-oxadiazolyl disulfide 2-mercapto-5 p-hydroxyphenyl) 1 3 ,4-oxadi azole ,uThiolfructoxazoline S-thiobenzoylthioglycolic acid II Q-oscrucoon 4-aminobenzotri-azole-HC1 S-oarbobenzoxy-L-cysteine NHn 21 Phenacylodithiocarbohydrazide l-mercapto-phthalazine S-nitro indazole N r NH N O z 2-pyridine carboxaldehyde thiosemicarbazo-ne Benzothiazolium methyl metho sulfate i13so4 OH; 1-methyl-2-mercaptoimidazole 3,4-diamino-5-mercapto-1,2,4-triazole 4-hydroxy-6-methyl-l,2,3a,7-tetrazaindene-3-thio1 CH3//N\\//NWN OH 7 5-phenyl-1,2,3a,4-tetrazaindene-7-thiol I 225 4-phenyliminothiourazole H N s1 Tm N -NH 5'-m ethy1-1,2,3a,4-tetraZaindene-7-thi0l 1,8-dibenzoyl-1$7.8-tetraza-4,5 dithia-3,6-dithionooctane N-N bis-(5-m-tolyl-1,3 ,4-oxadiazolyl) disulfide aji 5 ethy1-3 -mercapto-4-phenyl-1,2,4-triazole The above cyclic and open chain sulfur and nitrogencontaining tone modifying compounds share the common property, when employed in combination with the quaternary ammonium salts in the diffusion transfer processes, of causing the precipitation of the silver-containing images in a state of aggregation such that the images are neutral in color rather than brown or some other color. It is not apparent from the structures of these compounds nor from the structures of the host of other compounds, which are ineffective in combination with the quaternary (salts, to What factor the favorable result should be attributed. However, the tone-modifying effect does appear to be related to the fact that in the diffusion transfer processes the compounds all form with the silver halide of the emulsion, silver salts less soluble in water than silver chloride or silver bromide.

Representative developer compositions containing the combination of quaternary salt and tone modifying compound are given below.

EXAMPLE 16 Grams N-methyl-p-aminophenol sulfate 2.0 Hydroquinone 5.0 Sodium sulphite, des. 25.0 Sodium carbonate, IH O 30.0 Sodium thiosulphate, 5H O 10.0 5-bromo-6-methyl, 1,3,3a,7-tetraZaindene-4-thiol 0.2

Tetradecamethylene-bis-pyridinium perchlorate 0.2 Water to lliter. g r 1 1= 23 ment of the sensitive elements of the above Yackel et a1. invention, neutral toned images being obtained by development for two minutes at 68 F.

If either one or both of the organic materials, bromo-6-methyl 1,3,3a,7-tetrazaindene-4-thiol and tetradecamethylene-bis-pyridinium perchlorate, are omitted from the developer formula, a warm brown-toned image results.

The first five materials are dissolved in approximately 750 cc. of water at 90 F. The benzothiazolium methyl metho sulfate and the tetradecamethylene-bis-pyridinium perchlorate are dissolved in 50 cc. of warm water. The solutions are then added to the bulk solution which is then made up to one liter with cold water. The solution has a pH of approximately 10.1.

When this solution is employed in the same manner as the solution of Example 16, a neutral-toned image is obtained.

If either or both of the organic materials, benzothiazolium methyl metho sulfate and tetradecamethylene-bispyridinium perchlorate are omitted from the developer formula, a warmer toned image results.

EXAMPLE 18 A gelatin solution (250 cc.) was diluted with 750 cc. water. 2.5 cc. of 1 N Na S were then added to the solution. 250 cc. of water containing 2.6 cc. of 1 N zinc nitrate were added slowly to the sulfide solution through a jet, resulting in the formation of a colloidal dispersion of zinc sulfide. To this dispersion were added 10 liters of a 3% gelatin solution, 300 cc. of a 7.6% saponin solution and 134 cc. of a 10% formaldehyde solution. The mixture was dispersed at 40 C. and then coated on a photographic paper support at a coverage of 2 1b. of solution per 100 sq. ft. of coated surface and dried, forming the silver precipitating layer.

Over the silver precipitating layer was coated a 1% aqueous solution of the sodium salt (or other alkali metal salt) of cellulose ether phthalate (an ethyl cellulose containing 45.8% ethoxyl phthalated to 22.7% phthalyl) at a coverage of 0.15 lb. per 100 square foot.

To 1 liter of a positive speed, sulfur sensitized, high contrast chlorobromide emulsion containing approximately 30 g. of gelatin and one mole of silver halide per liter, were added the following ingredients: (Such emulsions containing low gelatin content can be prepared by the procedures described in the MacWilliam US. patent application Serial No. 440,282, filed June 29, 1954, now US. Patent 2,756,148 granted July 24, 1956, and the Yutzy and Frame US. Patent 2,614,928, granted October 21, 1952).

30 cc. of a 50% aqueous solution of glycerine 30 cc. of a 7.6% saponin solution 12 /2 cc. of a solution containing .2 gm. of l-carboxymethyl 5 [(3-ethyl-2(3)-benzoxazolylidene)-ethylidene]-3-phenyl-2-thiohydantoin in 30 cc. of MeOH-l-l drop of triethylamine To the above mixture were added 5 liters of a 4% solution of the ammonium salt of the cellulose ether phthalate just mentioned dissolved in methyl alcohol. The mass was stirred at 30 C., thoroughly dispersed and then coated over the sodium salt of cellulose ether phthalate interlayer at a coverage of 600 sq. ft. per mole of silver halide and dried in the conventional manner.

After exposure to a subject the sensitive element was 24 processed for 60 to seconds at 68 F. in the following developer solution:

Grams Monomethyl-p-aminophenol sulfate 2.0- Hydroquinone 5.0 Sodium sulfite, anhydrous 25.0 Sodium carbonate monohydrate 30.0 Sodium thiosulfate, 5H O 10.0 S-Nitroindazole 0.1

3,6,9,12,15,18,21,24 octoxahexacosane-1,26-bis-(5- ethyl-Z-methyl-pyridinium-methane sulfonate) Water to 1 liter.

followed by washing with water at 35 C. for 20 to 30 seconds to remove the emulsion layer leaving a neutraltoned positive image on the receiving layer. If either the tone modifying compound, S-nitroindazole, or the quaternary ammonium salt, 3,6,9,12,l5,18,2l,24-octoxahexacosane 1,26,bis (5-ethyl-2-methylpyridiniummethane sulfonate), is omitted from the developer solution, an unacceptable, warm-toned positive image is obtained.

EXAMPLE 19 The process of Example 18 was carried out using the same developer solution but in which S-nitroindazole was replaced by benzothiazolium methyl metho sulfate in like amount to also obtain a neutral-toned image. The omission of either of the nitrogen-containing compounds from the developer solution yields a warm-toned positive image.

EXAMPLE 20 The procedure of Example 18 was carried out with a number of developer solutions in which the pyridinium salt was replaced with the same amount of each of the following cyclammonium quaternary salts:

Decamethylene-u,w-bis-(oxymethyl pryidinium perchlorate) Z-B-phenethylisoquinolinium bromide l-fl-phenethylquinolinium bromide 3,14-dioxahexadecane-1, l6-bis-(pyridinium methane sulfonate) 3-methyl-2-fl-phenethyl isoquinolinium bromide In each case the image obtained was neutral-toned.

The substitution of quaternary ammonium bases or salts which consist of an onium radical attached to short chain aliphatic groups instead of the compounds listed above, does not give the desired results. Formulas containing e.g. fl-hydroxyethyl trimethyl ammonium-p-toluene sulfonatc, tetramethyl ammonium bromide, tetraethyl ammonium bromide or tctra-n-propyl ammonium bromide in concentrations ranging from 0.2-0.4 g./l. produced images having very warm tone and low maximum density.

EXAMPLE 21 The procedure of Example 18 was carried out with a number of developer solutions in which 5-nitroindazole was replaced by the same amount of benzothiazolium methyl metho sulfate and the pyridinium salt replaced by one of the following cyclammonium quaternary salts:

Tetradecamethylene-bis (pyridinium perchlorate) a Dimethyldithiocarbamathoethyl N methyl pyridinium-p-toluene sulfonate Decamethylene-a,w-bis-(oxymethyl pyridinium perchlorate) 2-,8-phenethylisoquinolinium bromide 3,l4-dioxahexadecane-l,l6bis-(pyridinium methane sulfonate) l-methyl-Z-nonanoyl pryidinium-p-toluene sulfonate HeptoXymethyl-2,4,6-trimethyl pyridinium chloride Tetradecamethylene-bis-(trimethyl ammonium perchlorate) 3-methyl-2,[3-phenethyl isoquinolinium bromide 25 4,4,10.10 tetraoxo 4,10 dithiatr-idecane bis (pyridinium perchlorate) l-B-phenethylquinolinium bromide In each case the image obtained was neutral-toned.

EXAMPLE 22 The process of Example 18 was carried out with separate developing solutions except containing the following quaternary salts in place of the pyridinium salt of the Example 18 solution.

Develop- D max. Net Quaternary Salt ment Positive Increase Time, Image in minutes D max.

None (Control 1) 2 2. 34 1 methyl- 2 -nonanoyl pyridinium ptoluene sug oriatel .t ...t h i 2 2. 44 0. He toxyme y -2, rime y -pyr1- d i niumheliloride d th 2 2. 62 0.28 Deeamet 3 ene a,w ioxyme pyridinium perchlorate) 2 3.10 0. 66* Tetradeeamethylene bis (tri methylammonium perchlorate 2 2. 68 0. 3% l-fl-phenethyLa-pieolinium bromide. 2 2. 82 0. 48 3 methyl 2 fl phenethyl -1so qulnolinium bromide 2 2. 48 0. 14 None (Control II) 1% 1.55 n l-fl-phenethyl quinolinium brom 1% 2. 15 0. 60 Zfi-phenethyl }i1s'oq1:;ifiio1linium brom11de 1% 1. 90 0.35 3-rneth l-2-B-p ene y iso-quino inium bromide 1% 2. 10 0. 55*

The results given in Table I also demonstrate another new and unexpected result. Those solutions containing the quaternary ammonium salts marked with an asterisk produced colder and more neutral image tone than is produced by the control developers. This effect is quite striking in some cases Where tone is changed from a yellow brown to a cold black tone. This effect was not as great, however, when a tone modifying compound such as the S-nitroindazole is not present during processing. The results also show that quite unexpectedly the quaternary salts efifect a substantial increase in D max.

EXAMPLE 23 The inadequacy of the short chain quaternary ammonium salts to improve the tone of the solvent transfer images was demonstrated by carrying out the procedure of Example 18 except using tetramethylammonium chloride, tetra-n-propylammonium chloride and trimethylphenylammonium chloride respectively as the quaternary salt in the following solution, development being carried out for 2 min. at 68 F.

Grams Monomethyl-p-aminophenol sulfate 2.0 Hydroquinone 5.0 Sodium sulfite 25.0 Sodium carbonate monohydrate 30.0 Sodium thiosulfate pentahydrate 10.0 Quaternary ammonium salt 0.2 Benzothiazolium methyl metho sulfate--. 0.2

The results were that the tone of the image was still yellow-brown the same as when the short chain quaternary salt was absent from the solution.

It is possible in solvent transfer processes such as described above to use an acidic rather than alkaline developing solution thereby effecting improvements such as reduction in stain on the transfer prints. For this purpose the acidic solution may contain a metal salt as titanous chloride, a metal ion chelating compound such as ethylenediamine tetraacetic acid and a silver halide solvent such as hypo as follows:

Titanium trichloride solution (20%) 'cc 150 Ethylenediamine tetraacetic acid tetrasodium salt grams 100 Sodium thiosulfate.5H O do 20 Water to make liter 1 pH adjusted to 4.0.

A suitably exposed emulsion is immersed in the solution briefly, then squeegeed in contact with a receiving sheet such as described above until a silver image is formed in the receiving layer. Other chelating agents such as iminotriacetic acids, oxalic, tartaric, etc. may be substituted in the developer solution.

Another method for preparing developer compositions which are appreciably less alkaline than those prepared with caustic alkali or alkali carbonate, includes using an organic alkaline buffer compound as the source of alkali. The buifer compounds are reaction products of sulfur dioxide and amino alcohols such as 2-diethylamino ethanol sulfite, 2-aminoethanol sulfite, 2-ethylaminoethanol sulfite, Z-methylaminoethanol sulfite, Z-dimethylaminoethanol sulfite. One advantage of the use of the buffer compounds lies in the fact that they permit the preparation of highly concentrated developer solutions which can be diluted with as much as forty parts of water without appreciable loss in activity.

A representative formula containing the buffer compounds is as follows:

4-metl1yl-1-phenyl-3-pyrazolidone grams 1.6 Hydroquinone L. do 11.2 2-diethyl amino ethanol-sulfite buffer do 44.4 Z-methyl amino ethanol thiosulfate do 11.4 Benzothiazolium methyl metho sulfate do 0.4 Ammonium hydroxide (28 percent) ml 4.6

The composition can be diluted to one liter for use and as such has a pH of 9.8.

In a parallel investigation of other compounds effective in improving the tone of the argental images, it has been found that when certain common organic solvents such as the lower alcohols, ketones, amides, and water soluble ethers are employed in the developer solutions containing silver halide solvent in sufficient concentration of the ,Order 7 to 20% by volume, in combination with one of the many cyclic and open chain sulfur and nitrogen-conraining compounds above, a pronounced improvement in tone of the argental images is obtained which effect is comparable to that obtained by the combination of quaternary salt and the tone-modifying compounds. Examples of the preferred compounds are: alcohols-methyl alcohol, ethyl alcohol, ethylene glycol, glycerol; ketonesacetone; am-idesforrnamide, acetamide; ethersdioxane.

It has further been observed that certain water soluble amines are effective in darkening the tone of the argental images in silver halide diffusion transfer processes. The effective amines include the primary aliphatic amines containing a linear carbon chain of from 4 to 6 carbon atoms, that is, amines of the normal butyl to hexylamine series. Surprisingly, lower and higher members of the series e.g., propylamine and heptylamine, are ineffective. Other amines which are effective are the a,w-alkylene diamines containing from 8 to 12 carbon atoms in the alkylene chain separating the amino groups, as in the series from oc,w-0Ctyln6 diamine to a,w-dodecylene diamine. Also, one of the amino groups of the diamine may be replaced by a hydroxyl group as in the alkanolamines. In addition, benzylamine and cyclohexylamine are useful for the same purpose.

These amines are advantageously used in the developing solutions containing developing agent and silver halide solvent used for initiating development of the sensitive element, in concentrations up to about 0.5%.

Representative aliphatic amines thus useful are as follows:

1,8-diamino-n-octane l-amino-l0-hydroxy-n-decane 1,12-diamino-n-dodecane l-arnino-l l-hydroxy-n-undecane n-Butylarnine 'Benzylamine n-Amylamine 4-di-N-butylarninobutylamine 3,3 -diaminodipropylamine 11-amino-3 ,6,9-triazaundecanol 14-amino-3,6,9, l2-tetrazatetradeoanol 3,6,9,10-tetraza-1,4-tetradecanediol 3,6,9,l2-pentaza-1,17-heptadecanediol 2-aminoethanol 2-methylaminoethanol Methylimino-bis-proplyamine A preferred group of toning compounds useful with the above amines are the following:

2,3-dihydro-2,5 -dimethyl-1-phenyl-1,2,4-triaZole-3-thione Z-mercapto-S-phenyl-1,3,4-oxadiazle S-aminobenzotriazole 4-aminobenzotriazole S-chlorobenzotriazole S-bromobenzotriazole 1-phenyl-2-mercaptotetrazole Benzothiazolium methyl metho sulfate The amines, and combinations of amines with the above large number of tone modifying compounds, are especially useful for producing black-toned images in the processes of the mentioned Yackel et al. US. patent application Serial No. 86,705,

A representative developer composition especially usefully in those processes is as follows:

Water to 1 liter.

In other developer formulas containing silver halide developing agent and silver halide solvent, butylamine may be replaced in similar quantity by other amines such as disclosed above or one of the amines in combination with one of the above-mentioned sulfur and nitrogencontaining tone modifying compounds.

Examples of the use of an amine in conjunction with one of the tone modifying compounds are as follows:

The following developer solution was prepared:

Grams 4-methyl-1-phenyl-3-pyrazolidone 1.6 Hydroquinone 11.2

2-ethylaminoethanol sulfite addition compound 35.2

2-amino ethanoL- 2.5 5 -bron1o-6-methyl-l ,3 ,3a,7-tetrazaindene-4-thio 0.2 5-bromo-6-rnethyll,3,3a,l-tetrazaindene-4athiol 0.2

Water to 1 liter.

Prepared by reacting 1 mole of sulfur dioxide with 4 moles of 2-ethylaminoethan0l.

The sulfite addition compound can be replaced by sodium sulfite by adjustment of the developing agent and silver halide solvent concentrations. When the above solution was used to develop sensitive elements such as shown in the examples of Yackel et al. US. patent application Serial No. 586,705 for 2 minutes at 68 F.

20 neutral toned toned images are obtained. The omission of either Z-aminoethanol or the tetrazaindene compound from the developing solution results in images of inferior tone and quality.

The following formula may also be used in the same manner to produce neutral toned images:

Grams 4-methyl-l-phenyl-S-pyrazolidone 1.6 Hydroquinone 11.2 2-ethylaminoethanol sulfite addition product 35.2 Sodium thiosulfate-5H O 9.2 Methylimino bis-propylamine 4.0 Benzothiazolium methyl methosulfate 0.2

Water to 1 liter.

*Prepared by reacting 1 mole of sulfur dioxide with 4 moles of 2-ethylamtnoethanol.

If the tone modifying compound benzothiazolium methyl metho sulfate is omitted, a weak positive image is obtained. If, on the other hand, the methylimino bispropylamine is omitted, no positive image is obtained.

What we claim is:

1. In a process for the direct production of positive images in which a silver halide emulsion layer is developed, to produce a silver image and the residual undeveloped silver halide is caused to diffuse image-wise to a receiving stratum, and an argental image is formed in the stratum for said residual silver halide in the presence of a silver precipitating agent, the step of forming said argental image in contiguity with quaternary ammonium salt having a linear chain of at least seven atoms attached directly to a quaternary nitrogen atom and a compound of the class consisting of Z-merc apto- 1 -phenyl-tetrazole 2-mercapto-5-phenyl-1,3 ,4-oxadiazole Dihydro-1,4-benzothiazin-3-one 2- -pyridylbenzothiazoline hydrochloride 5-t-butyl-6-methyl-1,2,3 a,7-tetrazaindene-4-thiol 7 -seleno-1 ,3 ,4,6-tetrazaindene 2,6-dimethyl-1,3,3 a,7-tetrazaindene-4-thiol 5 ethyl-6-methyl-l ,2,3a,7-tetrazaindene-4-thiol Bis- 5-p-hydroxyphenyl-l ,3 ,4-oxadiazolyl) disulfide Z-mercapto-S- (p-hydroxyphenyl) -1,3,4-oxadiazole ,u-Thiolfnictoxazoline 4-oxo-2,3 ,3a,4,5,6-hexahydro-1.,3a-diaza-7-thiaindene S-aminobenzotriazole S-thio'oenzoylthioglycolic acid 4-aminobenzotriazole HCl S-c arb obenzoxy-L-cysteine 5-cl1loro-1,2,3 -b enzotriazole Bromobenzotriazole Ethylene thiourea Ethylene thiocyanate 2,4,6-trimercapto-1,3,5-triazine 4,6 -dimercapto-5 -aminopyrimidine -Thiol glucoxazoline 2,4,6-trithiouramil Bis- 2,3-dihydroxypropyl) -disulfide 3-amino-5-mercapto-1,2,4-triazole 4-aminomethyl-2-mercaptoimid azole 1- B-hydroxyethyl) -3-methylthiourea 3 -p-anisyl-1,2-dithia-cyclopentene-S-thione 2-mercapto-5-amino- 1,3 ,4-thiadiazole 3 -mercapto-5-methyl-1,2,4-triazole 3-mercapto-1,2,4-triazole Z-mercapto-S- (m-tolyl) -1,3,4-oxadiazole Z-mercapto-S- (o-tolyl) -1,3,4-oxadiazole Z-mercapto-S-(o-methoxyphenyl) -1,3,4-oxadiazole 2-mercapto-5-(p-methoxyphenyl) -1,3 ,4-oxadiazole 2-mercapto-5-(p-nitrophenyl) -1,3 ,4-0xadiazole 2-mercapto-5-(m-nitrophenyl) -1,3,4-oxadiazole B-Mercapto-propionic acid 1-phenyl-2( l -thioquinolone Z-mercapto-B-n aphthoxazole 3-phenyl rhodanine 29 1-cyclohexyl-5-mercaptotetrazole Dimethylcarbamyldimethyl-thiocarbamylsulfide Sym-tetra-a-pyridyl-bis- (formamidine -disu1fide -('y-pyridyl methylidene) -2-thiono-thiazolidone .\//-1,5-dipheny1-3-mercapto-4-methy1-1,2,4-thiazole 2-mercaptobenzoxazole 3-amino-6-keto-4-rnethyl-1-phenyl-2-thiono-1,2,3,6

tetrahydropyrimidine 2-thionothiazolidone 2-mercaptobenzothiazole ,B-Picolyl-dimethyldithiocarbamate Thiobenzanilide 3-hydroxymethyl-2-thio-benzothiazolone Bis-2-thiazolyldisulfide 2-aminothiazoline Bis-2-benzoxazolyldisulfide 3,5-dimethyltetrahydro-1,3,5-2H-thiadiazine-2-thione 4-methyl-1,2,3a,7-tetrazaindene-6-thiol 2- 6-methy1- 1 ,3 ,3 a,7-tetrazainden-4-yl-thio ethylthiuronium bromide 6-methy1-1,2,3a,7-tetrazaindene-4-thiol 4,6-diaza-1-diethylamino-5-thioclecane Tetrapropyl thiuram disulfide l-benzyl-3,3-dimethylthiourea Thiodiglycolic dihydrazide 3-fi-pyridylpropyldimethyldithiocarbamate 5-bromo-6-methyl-1,3,3a,7-tetrazaindene-4-thiol 2,4,6-tris( diethylamino-ethylamino) -s-triazine 3HCl 4-hydroxy-1,3,8-triazanaphthalene 4-thiono-4a-azanaphthalene Z-mercapto-S-furyl-1,3,4-thiadiazole Z-mercaptobenzimidazole Z-mercapto pyridine-N-oxide 2-isothioureido pyridine-N-oxide 2-mercapto-5-methyl-4H,1,3,4-thiadiazine 2,3-dihydro-2,5-dimethyl-1-phenyl-1,2,4-triazole 3-thione 4,5-dihydro-1-(4,5-dihydroimidaZole-2-yl)-2-thior1o-imidazole Ethylene trithiocarbonate 3,4-diphenyl-5-mercapto-1,2,4-triazole Dimethylethylenediaminebiscarbodithioate 5-p-dimethylaminobenzylidine-2-thio-2,4oxazolidinedione 6-hydroxy-2-mercapto-4-methylpyridimine 3-B-forrnamidoethyl-S-mercapto-1,2,4-triazo1e 1-- -hydroXypropy1-3-methylthiourea Z-imino-S-thio-1,3,4-thiadiazolidine 5-imino-3-thiourazole Bis- [2- 4-pyridyl) -ethyl] -sulfide Phenacylodithiocarbohydrazide l-mercapto-phthalazine Z-(B-phenethylthio)-5-mercapto-1,3,4-thiadiazole 4-mercapto-1-thia-3,5,7-triazaindene a-Picolyldimethylclithiocarbamate S-nitro indazole 30 2-pyridine carboxaldehyde thiosemicarbazone Benzothiazolium methyl metho sulfate 1-methy1-2-mercaptoimidazole 3,4-diamino-5-rnercapto-1,2,4-triazole 4-hydroXy-6-rnethyl-1,2,3a,7-tetrazaindene-3-thiol 5-phenyl-1,2,3a,4-tetrazaindene-7-thiol 4-phenyliminothiourazole S-methyl-1,2,3a,4-tetraZaindene-7-thiol 1,8-dibenZ0yl-1,2,7,8-tetraza-4,5-dithia-3,6-dithionooctane Aminothiatriazole Bis-(5-m-t0lyl-1,3 ,4-oxadiazolyl disulfid e, and 5-ethyl-3-mercapto-4-phenyl-1,2,4-triazole.

2. The process of claim 1 wherein the quaternary ammonium salt is a cyclammonium quaternary ammonium salt.

3. The process of claim 1 wherein the quaternary ammonium salt is a member of the class consisting of:

Tetradecarnethylene-bis-(pyridinium perchlorate) a-Dimethyldithiocarbamatoethyl-N-rnethyl pyridinium p-toluene sulfonate N-methyl-2-N-propyl mercapto pyridinium perchlorate Decamethylene-a,w-bis-(oxymethyl pyridinium perchlorate) 3,6,9,12,15,18,21,24 octaoxahexacosane 1,26 bis-(5- ethyl-Z-methyl pyridinium methane sulfonate) 2-fi-phenethylisoquinolinium bromide l-fi-phenethylquinolinium bromide 3,14-dioXaheXadecane-1,16 his (pyridinium methane sulfonate) l-rnethyl-Z-nonanoyl pyridinium-p-toluene sulfonate Heptoxymethyl-2,4,6-trimethyl pyridinium .chloride Tetradecamethylene-bis-(trimethyl ammonium perchlorate) 3-methyl-2-fi-phenethyl isoquinolinium bromide 1-,8-phenethyl-a-picoliniurn bromide 4,4,10,10-tetraoXo-4,IO-dithiatridecane bis(pyridinium perchlorate) Z-fl-hydroxyethyl-l-ethyl quinolinium iodide References Cited in the file of this patent UNITED STATES PATENTS 2,197,809 McQueen Apr. 23, 1940 2,271,623 Carroll Feb. 3, 1942 2,275,727 Carroll Mar. 10, 1942 2,289,367 Kendall July 14, 1942 2,699,393 Weyde Jan. 11, 1955 2,725,298 Yutzy et al. Nov. 29', 1955 2,848,330 Chechak Aug. 19, 1958 2,886,437 Piper May 12, 1959 OTHER REFERENCES Henn et al.: Photographic Science and Technique, PSA

Tech. Quarterly, November 1954, pp. 126-130. 

1. IN A PROCESS FOR THE DIRECT PRODUCTION OF POSITIVE IMAGES IN WHICH HA SILVER HALIDE EMULSION LAYER IOS DEVELOPED TO PRODUCE A SILVER IMAGE AND THE RESIDUAL UNDEVELOPED SILVER HALIDE IS CAUSED TO DIFFUSE IMAGE-WISE TO A RECEIVING STRATUM, AND AN ARGENTIAL IMAGE IS FORMED IN THE STRATUM FOR SAID RESIDUAL SILVER HALIDE IN THE PRESENCE OF A SILVER PRECIPITATING AGENT, THE STEP OF FORMING SAID ARGENTAL IMAGE IN CONTIGUITY WITH QUATERNARY AMMONIUM SALT HAVING A LINEAR CHAIN OF AT LEAST SEVEN ATOMS ATTACHED DIRECT TO A QUATERNARY NITROGEN ATOM AND A COMPOUND OF THE CLASS CONSISTING OF 2-MERCAPTO-1PHENYL-TETRAZOLE 2-MERCAPTO-5-PHENYL-1,3,4-OXADIAZOLE DIHYDRO-1,4-BENZOTHIAZIN-3ONE 2-Y-PYRIDYLBENZOTHIAZOLINE HYDROCHLORIDE 5-T-BUTY-6-METHYL-1,2,3A,7-TETRAZAIONDENE-4-THIOL 7-SELENO-1,3,4,6-TETRAZAINDENE I,L-DIMETHYL-1.3,3A,7-TETRAZAINDENE-4-THIOL 5-ETHYL-6-METHYL-1,2,3A,7-TETRAZAINDENE-4-THIOL BIS-(5-P-HYDROXYPHENYL-1,3,4-OXADIAZOLYL)DISULFIDE 2-MERCAPTO-5-(P-HYDROXYPHENYL)1,3,4-OXADIAZOLE U-THIOLFRUCTOXAZOLINE 4-OXO-2,3,3A,4,5,6-HEXAHYDRO-1,3A-DIAZA-7-THIAINDENE 5-AMINOBENZOTRIAZOLE S-THIOBENZOYLTHIOGLYCOLIC ACID 4-AMINOBENZOTRIAZOLE.HCL S-CARBOBENZOXY-L-CYSTEINE 5-CHLORO-1,2,3-BENZOTRIALZOLE BROMOBENZOTRIAZOLE ETHYLENE THIOUREA ETHYLENE THIOCYANATE 2,4,6-TRIMERCAPTO-1,3,5-TRIAZINE 4,6IDIMERCAPTO-5-AMINOPYRIMIDINE U-THIOLGLUCOXAZOLINE 2,4,6-TRITHIOURAMIL BIS-(2,3-DIHYDROXPROPYL)-DISULFIDE 3-AMINO-5-MERCAPTO-1,2,4-TRIAZOLE 4-AMINOMETHYL-2-MERCAPTIOMIDAZOLE 1-(B-HYDROXYETHYL)-3-METHYLTHIOUREA 3-P-ANISYL-1,2,-DITHIA-CYCLOPENTENE-5THIONE 2-MERCAPTO-5-AMINO-1,3,4-THIADIAZOLE 3-MERCAPTO-5-MWTHYL-1,2,4-TRIAZOLE 3-MERCAPTO-1,2,4-TRIAZOLE 2-MERCAPTO-5-(M-TOLYL)-1,3,4-OXADIAZOLE 2-MERCAPTO-(O-TOLYL)-1,3,4-OXADIAZOLE --MERCAPTO-5-(O-METHOXPHENYL)1,3,4-OXADIAZOLE 2-MERCAPTO-5-P-METHOXYPHENYL)-1,3,4-OXIDIAZOLE 2-MERCAPTO-5-(P-NITROPHENYL)-1,3,4-OXIDIAZOLE 2-MERCAPTO-5-(M-NITROPHENYL)-1,3,4-OXIADIAZOLE B-MERCAPTO-PROPIONIC ACID 1-PHENYL-2(1)-THIOQUIMOLONE 2-MERCAPTO-B-NAPHTHOXAZOLE 3-PHENYL RHODANINE 1-CYCLOHEXYL-5-MERCAPTOTETRAZOLE DIMETHYLCARBAMYLDIMETHYL-THIOCAMBAMYLSULFIDE SYM-TETRA-A-PYRIDYL-BIS-(FORMAMIDINE)-DISULFIDE 5-(Y-PYRIDYL METHYLIDENE)-2-THIONO-THIAZOLIDONE $-1,5-DIPHENYL-3-MERCAPTO-4-METHYL-1,2,4-THIAZOLE 2-MERCAPTOBENZOXAZOLE 3-AMINO-6-KETO-4-METHYL-1-PHENYL-2-THIONO-1,2,3,6TETRAHYDROPYRIMIDINE 2-THIONOTHIAZOLIDONE 2-MERCAPTOBENZOTHIAZOLE B-PICOLYL-DIMETHYLDITHIOCARBAMATE THIOBENZANILIDE 3-HYDROXYMETHYL-2-THIO-BENZOTHIAZOLONE BIS-2-THIAZOLYLDISULFIDE 2-AMINOTHIAZOLINE BIS-2-THIAZOLYLDISULFIDE 3,5-DIMETHYLTERTRAHYDRO-1,3,5-2H-THIADIAZINE-2-THIONE 4-METHYL-1,2,3A,7-TETRAZAINDENE-6-THIOL 2-(6-METHYL-1,3,3A,7-TETRAZAINDEN-4-YL-THIO)ETHYLTHIURONIUM BROMIDE 6-METHYL-1,2,3A,7-TETRAZAINDENE-4-THIOL 4,6-DIAZA-1-DIETHYLAMINO-5-THIODECANE TETRAPROPYL THIURAM DISULFIDE 1-BENZYL-3,3-DIMETHYLTHIOUREA THIODIGLYCOLIC DIHYDRAZIDE 3-B-PYRIDYLPROPYLDIMETHYLDITHIOCARBAMATE 5-BROMO-6-METHYL-1,3,3A,7-TETRAZAINDENE-4THIOL 2,4,6-TRIS(DIETHYLAMINO-ETHYLAMINO)-S-TRIAZINE.3HCL 4-HYDROXY-1,3,8-TRIAZANAPHTHALENE 4-THIONO-4A-AZANAPHTHALENE 2-MERCAPTO-5-FURYL-1,3,4-THIADIAZOLE 2-MERCAPTOBENZIMIDAZOLE 2-MERCAPTO PYRIDINE-N-OXIDE 2-ISOTHIOUREIDO PYRIDINE-N-OXIDE 2,3-DIHYDRO-2,5-DIMETHYL-1-PHENYL-1,2,4-TRIAZOLE 3-THIONE 2,3-DIHYDRO-2,5-DIMETHYL-1-PHENYL-1,2,4-TRIAZOLE 3-THIONE 4,5,-DIHYDRO-1-(4,5-DIHYDROIMIDAZOLE-2-YL)-2-THIONO-IMIDAZOLE ETHYLENE TRITHIOCARBONATE 3,4-DIPHENYL-5-MERCAPTO-1,2,4-TRIAZOLE DIMETHYLETHYLENEDIAMINEBISCARBODITHOATE 5-P-DIMETHYLAMINOBENZYLIDINE-2-THIO-2,4-OXAZOLIDINEDIONE 6-HYDROXY-2-MERCAPTO-4-METHYLPRIDIMINE 3-B-FORMAMIDOETHYL-5-MERCAPTO-1,2,4-TRIAZOLE 1-Y-HYDROXYPROPYL-3-METHYLTHIOUREA 2-IMINO-5-THIO-1,3,4-THIADIAZOLIDINE 5-IMINO-3-THIOURAZOLE BIS-(2-(4-PYRIDY)-ETHYL)-SULFIDE PHENACYLODITHIOCARBOHYDRAZIDE 1-MERCAPTO-PHTHALAZINE 2-(B-PHENETHYLTHIO)-5-MERCAPTO-1,3,4-THIADIAZOLE 4-MERCAPTO-1-THIA-3,5,7-TRIAZAINDENE A-PICOLYLDIMETHYLDITIOCARBAMATE 5-NITRO-INDAZOLE 2-PYRIDINE CARBOXALDEHYDE THIOSEMICARBAZONE BENZOTHIAZOLIUM METHYL METHO SULFATE 1-METHYL-2-MERCAPTIOMIADAZOLE 3,4-DIAMINO-5-MERCAPTO-1,2,4-TRIAZOLE 4-HYDROXY-6-METHYL-1,2,3A,7-TETRAZAINDENE-3-THIOL 5-PHENYL-1,2,3A,4-TETRAZAINDENE-7-THIOL 4 PHENYLIMINOTHIOURAZOLE 5-METHYL-1,2,3A,4-TETRAZAINDENE-7-THIOL 1,8-DIBENZOYL-1,2,7,8-TETRAZA-4,5-DITHIA-3,6-DITHIONOOCTANE AMINOTHIATRIAZOLE BIS-(5-M-TOLYL-1,3,4-OXADIAZOLYL)DISULFIDE, AND 5-ETHYL-3-MERCAPTO-4-PHENYL-1,2,4-TRIAZOLE. 